Profiled roller bearing

ABSTRACT

The invention relates to a roller bearing in which high edge stresses resulting from shaft misalignment can be mitigated or overcome. The invention provides a roller bearing comprising an inner, an outer ring and a plurality of bearing rollers disposed therebetween wherein the outer bearing ring has an axial end face and a grooved formed therein, the groove extending longitudinally about the axis of rotation of the bearing. The groove may be formed between the radially inner and outer edges of the end face or may be formed at the radially outer edge, and have the form of a chamfer. The groove may be continuous or discontinuous around the end face.

[0001] This invention relates to a roller bearing assembly and inparticular, though not exclusively, to a gear unit comprising a housingand gear shafts rotatably supported relative to the. housing by means oftaper or cylindrical roller bearings.

[0002] In accordance with the recommendations of bearing manufacturersit is conventional to provide a shrink type fit between the inner ring,(cone), of a taper roller bearing and the surface of a gear shaft. Theshrink fit is necessary in order to avoid or minimise the risk offretting corrosion and other damage.

[0003] In contrast to the shrink fit requirement for the inner ring, theouter ring of a roller bearing of the taper type does not need to be atight fit in the housing because of the point type loading experiencedby the outer ring.

[0004] Whilst a shrink fit is not required between the outer ring ofeach bearing and the housing wall, the housing wall neverthelessrequires to be sufficiently stiff-in order that the bearing is properlylocated axially and in order that required preload or clearance ismaintained despite axial forces arising in consequence of any helicalgear carried by a shaft and which would tend to distort a housing wall.

[0005] The operating life of bearings of both the taper and cylindricalroller types is dependant also on the degree of misalignment which mightarise in use between the rotational axis of the shaft to which the innerbearing ring is secured, and the location of the outer bearing ring.Particularly in the case of those gear stages of a multistage gear boxthat are subject to higher loads, the shaft misalignment can besignificant and the consequential high edge stresses experienced by thebearing can result in an undesirable reduction in the satisfactoryworking life of the bearing.

[0006] The present invention seeks to provide a rollerbearing assemblyin which the aforedescribed difficulties are mitigated or overcome.

[0007] In accordance with one aspect of the present invention there isprovided a roller bearing comprising an inner ring, an outer ring. and aplurality of bearing rollers disposed therebetween wherein the outerbearing ring has an axial end face and a groove formed therein.

[0008] Said groove may be circumferentially continuous, or, in e.g. acase in which the outer ring is intended to be loaded in use primarilyonly in one or a limited angular range of directions, it may extendaround only part of the end face, about the axis of rotation of thebearing.

[0009] The axial depth of the groove, as considered in a directionparallel with the axis of rotation of the bearing, preferably tiesbetween 10% and 75%, more preferably between 15% and 50% of the axiallength of bearing outer ring.

[0010] The roller bearing may be of the type comprising cylindricalrollers, or tapered rollers. In the case of a taper roller bearing, forwhich the radial dimension of the end face of the outer ring is greaterat one axial end of the outer ring than at the other end, it may bearranged that in use the point of maximum stress in the bearing occursin the vicinity of that end of the bearing having the greater radialdimension to the outer ring, and the groove may be formed in said endface of greater radial dimension. The invention does not exclude,however, provision of a groove at the smaller radial end of the outerring of a tapered roller bearing.

[0011] For both cylindrical and taper type roller bearings a groove maybe provided in either one or each of the axial end faces of the outerring.

[0012] The invention teaches also that the groove may be in the form ofa chamfer provided at the radially outer surface of the bearing outerring. Thus whilst conventionally an outer ring has a cylindricalradially outer shape, in accordance with the present invention it isprovided that the cylindrical shape may extend along only part of theaxial length of the outer surface, with the remaining axial lengthdeparting from said cylindrical shape, for example to be of afrusto-conical shape.

[0013] In accordance with a further aspect of the present inventionthere is provided a roller bearing assembly comprising a housing whichdefines a tubular housing formation and a roller bearing having theouter ring of the roller bearing located within said tubular housingformation, an axial end face of the assembly, as considered in an axialdirection parallel with the axis of rotation of the bearing. comprisinga groove positioned radially between the radially inner surface of thebearing outer ring and the radially inwardly facing surface of thetubular housing formation.

[0014] Said groove may be defined by axially extending groove side wallsformed in the outer ring of the bearing or may be defined in part by theouter surface of the bearing outer ring and in part by said radiallyinwardly facing surface of the tubular housing formation.

[0015] The radial dimension of the groove preferably is less than 70%,more preferably less than 60% of the radial thickness of the outer ringas considered at local axial positions between the axial ends of theouter ring.

[0016] Examples of cross-sectional shapes of a groove include a square,rectangular and triangular shape, but it is to be understood that othershapes or combinations of shapes may be employed. Similarly, in the caseof a groove defined in. an assembly by a space between the outer ringand the aperture of a housing formation, the aforementioned shape anddimensional features of a groove formed within an outer ring of abearing similarly may be employed.

[0017] The thickness of the outer ring between the radially innerraceway surface and the groove formed in the thickness of the ring orthe shape and/or the manner in which the housing supports the ring overonly part of the axial length of the bearing ring thereby may assist inallowing the raceway to deform elastically under load in a manner whichtends to follow distortion of the shaft when operating under load.

[0018] Embodiments of the present invention will now be described, byway of example only, with reference to the accompanying diagrammaticdrawings in which:

[0019] FIGS. 1 to 3 each show in cross-section part of a tapered rollerbearing in accordance with the present invention;

[0020]FIG. 4 shows part of a cylindrical roller bearing in accordancewith the present invention; and

[0021]FIG. 5 shows part of a bearing assembly in accordance with thepresent invention.

[0022]FIG. 1 shows the outer ring 9 and a taper roller 13 forming partof a taper roller bearing 8 rotatable about an axis 7.

[0023] The outer ring 9 comprises a radially outer cylindrical surface11 and a frusto-conical radially inwardly facing surface 12 over whichthe roller 13 rotates.

[0024] The outer ring 9 has an end face 14 of greater radial dimensionthan the other end face 15. The end face 14 is formed with acircumferentially continuous groove 10 the radial dimension w of whichis less than 10% of the local radial thickness We of the ring 9 at allaxial positions of the groove. The groove depth d being axial length ofthe groove as considered in a direction parallel with the axis 7 in thisembodiment is approximately 25% of the axial length 1 of the outer ring9. The groove of this embodiment has a substantially rectangular shape,comprising a pair of parallel side walls and a base which formanufacturing convenience and to avoid stress concentrations is of aslightly curved profile.

[0025]FIG. 2 shows variation of the embodiment of FIG. 1 in which thebearing outer ring comprises between radially outer and inner faces 11,12 a circumferentially continious groove 20 of a substantiallytriangular shape in common with the groove of the FIG. 1 embodiments thegroove 20 has a slightly curved base region to avoid stressconcentrations.

[0026]FIG. 3 shows a variation in which the radially outer surface 11 ofthe outer ring is cylindrical over any part of the axial length and forthe remainder 24 is cut away to provide a recess region 30.

[0027]FIG. 4 shows a construction substantially similar to that of FIG.2, but comprising a cylindrical roller bearing 34 and a groove 40 oftruncated triangular shape provided in one of the axial end faces of thebearing outer ring. FIG. 5 illustrates a bearing assembly comprising abearing outer ring 51 and a taper roller 52 with the bearing outer ring51 located within a tubular aperture formation defined by a housing 53.

[0028] The bearing outer ring 51 has a cylindrical shape over a part 55of the axial length thereof, and said part of the outer ring is tightfit in a cylindrical portion 54 of the aperture defined by the housing53.

[0029] The remainder of the axial length of the outer surface of thebearing outer ring 51 is comprised by a frusto-conical shape surface 57.Similarly, the remainder of the axial length of the aperture of thehousing 53 is defined by a frusto-conical shape surface 56. A grooveregion 58 is thereby formed between the confronting surfaces 56, 57. Inuse of the bearing when subjected forces caused by bending of a shaftrotatably carried by the bearing, the end of the bearing outer ring 51in a vicinity of the frusto-conical surface 57 is able to elasticallydeform radially outwards more readily than the part of the bearing outerring contained within the cylindrical surface portion 54, and theoccurrence of localised and undesirable stress concentrations on thebearing, in particular between the roller 52 and radially inner surfaceof the outer ring, is there by reduced or avoided.

1. A roller bearing (8) comprising an inner ring, an outer ring (9,51)having two axial end faces (14,15). and a plurality of tapered bearingrollers (13,52) disposed therebetween wherein the outer bearing ring hasan a circumferentially continuous groove (10,20,30,40.58) formed in thataxial end face (14) having the greater radial dimension, the groove(10,20,30,40,58) extending longitudinally about the axis of rotation (7)of the bearing.
 2. A roller bearing according to claim 1 wherein thegroove is formed at the radially outer edge of the end face.
 3. A rollerbearing according to claim 1 wherein the groove is formed between theradially inner and radially outer edges of the end face (14).
 4. Aroller bearing according to any of the preceding claims wherein theaxial depth (d) of the groove (10.20,30,40,58) is between 10% and 75% ofthe axial length (1) of the outer ring (9,51).
 5. A roller bearingaccording to claim 4 wherein the axial depth (d) of the groove(10,20,30,40,58) is between 15% and 50% of the axial length (1) of theouter ring (9,51).
 6. A roller bearing according to any of the precedingclaims wherein the radial dimension (w) of the groove (10,20,30,40,58)is less than 70% of the radial thickness (We) of the outer ring (9,51)as considered at local axial positions between the axial ends (14.15) ofthe outer ring (9,51).
 7. A roller bearing according to claim 6 whereinthe radial dimension (w) of the groove (10,20,30,40,58) is less than 50%of the radial thickness (We) of the outer ring (9,51) considered atlocal axial positions between the axial ends (14,15) of the outer ring(9,51).
 8. A roller bearing according to any of the previous claimswherein a groove (10,20,30,40,58) is formed in both axial end faces(14,15) of the outer ring (9,51).
 9. A roller bearing substantially asdescribed herein and depicted in FIGS. 1 to
 5. 10. A roller bearingassembly comprising a housing which defines a tubular housing formationand a roller bearing having the outer ring of the roller bearing locatedwithin said tubular housing formation. an axial end face of theassembly, as considered in an axial direction parallel with the axis ofrotation of the bearing, comprising a groove position radially betweenthe radially inner surface of the bearing outer ring and the radiallyinwardly facing surface of the tubular housing formation.
 11. A rollerbearing assembly according to claim 10 wherein the groove is defined inpart by the radially inwardly facing surface of the tubular housingformation.
 12. A roller bearing assembly according to either of claims10 or 11 comprising a bearing inner ring which is a shrink fit on ashaft
 13. A roller bearing assembly according to any of claims 10 to 12wherein the outer ring is not a tight fit in the housing.
 14. A rollerbearing assembly as substantially described herein and depicted in FIGS.1 to 5.